如何从httputil.ReverseProxy创建URL重写？

I'm trying to create a url rewrite reverse proxy in golang by httputil.ReverseProxy which similar to nginx reverse proxy

location /app {
   proxy_pass http://127.0.0.1:8080;
}

It passes all path with prefix /app/includes/subpath to http://127.0.0.1:8080/includes/subpath

How can I pass recursive url path (<prefix>/pass/from/subpath/to/other/services/) to http.HandleFunc ?

r := mux.NewRouter().StrictSlash(false)
r.HandleFunc("/proxy/*", func(w http.ResponseWriter, r *http.Request) {
        log.Print(r.URL)
        proxy.ServeHTTP(w, r)
    })

proxy is based on original source code from httputil https://golang.org/src/net/http/httputil/reverseproxy.go#L108

package main

import (
    "fmt"
    "log"
    "net/http"
    "net/http/httputil"
    "net/url"
    "strings"

    "github.com/gorilla/mux"
)

func singleJoiningSlash(a, b string) string {
    aslash := strings.HasSuffix(a, "/")
    bslash := strings.HasPrefix(b, "/")
    switch {
    case aslash && bslash:
        return a + b[1:]
    case !aslash && !bslash:
        return a + "/" + b
    }
    return a + b
}

func NewURLRewriteReverseProxy(target *url.URL) *httputil.ReverseProxy {
    targetQuery := target.RawQuery
    director := func(req *http.Request) {
        // debug

        req.URL.Scheme = target.Scheme
        req.URL.Host = target.Host
        req.URL.Path = singleJoiningSlash(target.Path, req.URL.Path)
        if targetQuery == "" || req.URL.RawQuery == "" {
            req.URL.RawQuery = targetQuery + req.URL.RawQuery
        } else {
            req.URL.RawQuery = targetQuery + "&" + req.URL.RawQuery
        }
        if _, ok := req.Header["User-Agent"]; !ok {
            // explicitly disable User-Agent so it's not set to default value
            req.Header.Set("User-Agent", "")
        }

        log.Println(req.URL, req.URL.Path)
    }

    return &httputil.ReverseProxy{Director: director}
}

func main() {
    r := mux.NewRouter().StrictSlash(false)
    origin, _ := url.Parse("http://httpbin.org")

    proxy := NewURLRewriteReverseProxy(origin)
    // proxy := httputil.NewSingleHostReverseProxy(origin)

    r.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprint(w, "hello")
    })


    // How can I write the regex or url path in this handler ?
    r.HandleFunc("/proxy/{name}/", func(w http.ResponseWriter, r *http.Request) {
        proxy.ServeHTTP(w, r)
    })

    log.Fatal(http.ListenAndServe(":9001", r))
}